Fluid amplifier controlled carburetor

ABSTRACT

A carburetor with a fluid amplifier, controlled by venturi signal, to pressurize the float bowl in inverse proportion to the air flow through the mixture conduit and thereby augment fuel delivery through the main metering system during engine idling.

United States Patent York, Jr. Apr. 18, 1972 [54] FLUID AMPLIFIER CONTROLLED [56] 7 References Cited CARBURETOR UNITED STATES PATENTS [72] Imam" JmmeB' Rmloak 2,009,412 7/1935 Prentiss ..261/D1G. 67 [73] Assignee: General Motors Corporation, Detroit, 3,307,837 3/1967 Winkler..... 26l/DlG. 67 Mich. 3,388,898 6/1968 Wyczalek... 261/DlG. 69 1,329,309 l/l920 Prentiss ..261/72 1 Flledi J11"e 1970 1,984,382 12/1934 Prentiss ..261/DIG. 67 [21] APPLNOJ 56,080 3,302,935 2/1967 York, Jr ..26l/36A Related s A li ati Data. Primary Examiner-Tim R. Miles 7 Attorney.lean L. Carpenter and Charles K. Veenstra [63] Continuation of Ser. No. 764,907, Oct. 3, 1968, abandoned. 57 ABSTRACT A carburetor with a fluid amplifier, controlled by venturi [52] "261/72 261mm? 3 3$? signal, to pressurize the float bowl in inverse proportion to the Int Cl F02! 5/08 air flow through the mixture conduit and thereby augment fuel 58 Field ofSearch ..261/DlG. 67,DIG. 69, 72 R; $1 ,35 thmugh the mam mete'mg System du'mg engme 1 Claim, 1 Drawing Figure e i AlR 511F 98 PUMP FLUID AMPLIFIER CONTROLLED CARBURETOR RELATED APPLICATION This is a continuation of copending application Ser. No. 764,907, filed Oct. 3, 1968, and now abandoned.

BACKGROUND OF THE INVENTION My invention relates to carburetors for metering the delivery of fuel to internal combustion engines, and particularly to improvements in the means for regulating the fuel delivery at low engine operating speeds. In accordance with the invention I use a closed fuel supply chamber, or float bowl, and introduce air thereinto from an external pressure source toiaugment the normal rate of aspiration of the fuel by the combustion supporting air passing through the carburetor as the rate of such flow falls off at low engine speeds.

While it is not new to use an unvented float bowl wherein the pressure above the fuel level is controlled in accordance with either engine intake vacuum or carburetor air flow rate, such prior arrangements of which I am aware have been directed to means for reducing rather than increasing the pressure on the float bowl fuel. Thus, in my prior US. Pat. No. 3,386,710 a partial vacuum is maintained above the fuel within the bow] at all times during engine operation, and in US. Pat. No. 2,796,243 to McDuffie the float bowl is subjected to engine intake vacuum to reduce fuel delivery during engine deceleration.

By reversing the process, i. e. by pressurizing the float bowl instead of subjecting it to a vacuum, I have found that the desired degree of control of the fuel/air ratio necessary for proper operation of the engine can be obtained in more simplified manner.

BRIEF DESCRIPTION OF THE DRAWING The single drawing figure shows rather schematically a sectional view of a carburetor embodying the invention and mounted on an intake manifold of an internal combustion engine.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring to the drawing, the carburetor 1 is of the downdraft type and is bolted at its lower end to the inlet 2 of an engine intake manifold 3. Combustion supporting air for the engine passes through the main carburetor air passage 4 under the control of the usual butterfly type throttle valve 5. This passage has a venturi shape which creates a partial vacuum or depression at the throat 7 in response to the flow of air therethrough. At one side of the main air passage 4 is a closed fuel reservoir or float bowl 8 into which fuel is introduced via the fuel inlet conduit 9 by a pump (not shown) from a larger supply tank. The intake of fuel by the bowl 8 may be regulated by the usual valve 10 carried by the float 11 to maintain the desired level 12 of the fuel. A duct 13 connects the bowl 8 below the fuel level 12, with the main air passage 4 at the venturi throat 7. Fuel is thus aspirated through the duct 13 to mix with the air entering the engine, at a rate which increases generally with the air flow rate through the passage 4. At the entrance to the duct within the float bowl is shown an orifice plate 14 which limits the rate of such fuel flow in relation to the air flow.

To maintain a sufficiently higher pressure on the fuel within the float bowl than exists in the venturi throat to effect such aspiration on the fuel, I introduce air under pressure into the upper part of the bowl from an external source such as an air supply pump indicated by the numeral 15. Passage means 16 is provided which is connected at one end to this pressure air source and includes branch passages 17 and 18 leading to an atmospheric vent 19 and the upper end of the float bowl, respectively. The angularity of these branch passages, as shown, is such that part of the pressure airstream may enter the branch passage 17 and be discharged to exhaust through the atmospheric vent 19, and part thereof may enter the float bowl via the branch passage 18. Such latter part, entering the float bowl will apply pressure to the fuel therein and assist its aspiration through the duct 13 into the airstream passing through the main air passage 4 of the carburetor. During operation of an engine at speeds substantially above its idling speed the air pressure within the float bowl need only be maintained at or about atmospheric pressure, because the flow of air into the engine through the main passage 4 is then at a high enough level that sufficient vacuum is created in the venturi throat 7 to aspirate enough fuel through the duct to maintain the fuel/air ratio required for such operation. When the air flow rate is relatively low, however, as during engine idling, the venturi vacuum is insuflicient to aspirate fuel, which in other carburetors is generally taken care of by extra idling fuel ducts. All of this is avoided in accordance with my invention by regulating fuel bowl pressure in accordance with the rate of carburetor air flow so as to augment the aspiration of fuel through the main metering duct 13 as the rate of air flow decreases. To accomplish this I provide signal passages 20 and 21 for the air flowing through the air passage 16, and utilize the decreasing pressure differential between these passages during reduction in engine speed to increase the pressure on the fuel in the float bowl. As shown, the lower end of passage 21 connects with the main air passage 4 at the venturi throat 7, and the upper end of passage 20 connects with the main air passage at a substantial distance upstream of the venturi throat. The passages 20, 21 also intersect the pressure air passage means 16 in the plane of and opposite the entrance to the branch passages 17 and 18, thereby attaining a fluid amplifying effect on the pressure airstream. During relatively high rates of air flow through the carburetor main air passage 4 there exists a correspondingly high pressure differential between the venturi throat 7 and the main air passage above the throat. This pressure differential acts on the pressure airstream flowing in the passage means 16 with sufficient force to deflect the major portion thereof into the branch passage 17 for discharge to atmosphere via the vent 19.

As the rate of flow of air through the main passage 4 decreases, such pressure differential also decreases with resultant lessening of the force on' the pressure airstream, and thus a greater portion of the pressure air is directed into the branch passage 18 leading to the float bowl. The increased pressure on the fuel in the bowl thereby compensates for the reduced aspirating effect of the lower flow rate of carburetor air in the main passage 4 to maintain the desired fuel flow.

It will be appreciated that various changes in the parts and their arrangement from that shown and described above may be made without departing from the spirit and scope of the invention as hereinafter claimed.

I claim:

I. A carburetor comprising a main air passage for air flow to the engine, a throttle rotatably disposed in said main air passage for controlling air flow therethrough, said throttle having a substantially closed idle position during conditions of minimum air flow through said main air passage, a venturi disposed in said main air passage for creating a vacuum signal which varies in accordance with air flow therethrough, a closed fuel reservoir, a fuel passage extending from said reservoir to said venturi for delivering fuel to said main air passage in accordance with said vacuum signal, said vacuum signal being insufficient to cause fuel flow through said fuel passage when said throttle is in said idle position, an atmospheric vent, a pump for supplying a stream of air under pressure, and a fluid amplifier including an inlet passage extending from said pump and first and second branch passages extending to said reservoir and said vent respectively for directing at least a portion of said air stream to pressurize said reservoir and for directing the remainder of said air stream to said vent, said fluid amplifier further including a first signal passage extending from said main air passage at a location upstream of said venturi to said inlet passage on the side thereof adjacent said first branch passage, said fluid amplifier also including a second signal passage extending from said venturi to said inlet portion thereof directed to pressurize said reservoir upon an increase in air flow through said main air passage caused by opening of said throttle from said idle position, whereby the increase in pressure in said reservoir when said throttle is in said idle position assists said vacuum signal in causing fuel flow through said fuel passage when said throttle is in said idle position. 

1. A carburetor comprising a main air passage for air flow to the engine, a throttle rotatably disposed in said main air passage for controlling air flow therethrough, said throttle having a substantially closed idle position during conditions of minimum air flow through said main Air passage, a venturi disposed in said main air passage for creating a vacuum signal which varies in accordance with air flow therethrough, a closed fuel reservoir, a fuel passage extending from said reservoir to said venturi for delivering fuel to said main air passage in accordance with said vacuum signal, said vacuum signal being insufficient to cause fuel flow through said fuel passage when said throttle is in said idle position, an atmospheric vent, a pump for supplying a stream of air under pressure, and a fluid amplifier including an inlet passage extending from said pump and first and second branch passages extending to said reservoir and said vent respectively for directing at least a portion of said air stream to pressurize said reservoir and for directing the remainder of said air stream to said vent, said fluid amplifier further including a first signal passage extending from said main air passage at a location upstream of said venturi to said inlet passage on the side thereof adjacent said first branch passage, said fluid amplifier also including a second signal passage extending from said venturi to said inlet passage on the side thereof adjacent said second branch passage, said signal passages thereby imposing a pressure differential across said air stream which varies in accordance with air flow through said main air passage, said pressure differential causing diversion of said air stream to increase the portion thereof directed to pressurize said reservoir upon a decrease in air flow through said main air passage caused by closure of said throttle to said idle position and to decrease the portion thereof directed to pressurize said reservoir upon an increase in air flow through said main air passage caused by opening of said throttle from said idle position, whereby the increase in pressure in said reservoir when said throttle is in said idle position assists said vacuum signal in causing fuel flow through said fuel passage when said throttle is in said idle position. 